| Alternate wetting and drying irrigation(AWD)can significantly reduce irrigation volume,increase or maintain rice yield and water productivity.However,under the alternate wetting and drying irrigation,the conversion and migration of nutrients are significantly different from traditional flood irrigation.Zeolite is a porous mineral with the characteristics of water retention,cation exchange and adsorption selectivity,and contains 3% to 5% of total potassium,which can provide a rich source of potassium for rice,and can also increase the content of available phosphorus in the soil.Therefore,this study used a split-zone test design to study the effects of zeolite on rice growth and phosphorus and potassium nutrient absorption,soil phosphorus and potassium nutrient migration and transformation,water consumption,water productivity and yield in alternately wet and dry irrigation paddy fields.While studying the migration and transformation of phosphorus and potassium in rice fields,it provides a new way for saving water and fertilizer in rice fields and improving the ecological environment.The main results are as follows:(1)Increasing the application of zeolite(5~10 t · hm-2)significantly increased the dry matter weight of aerial parts of rice during each growth period.Increasing the application rate to 10 t · hm-2 zeolite could significantly increase the number of tillers and the number of effective steer and output,the increase rate is 8.7% ~ 22.3%.In terms of the perspective of production composition,zeolite increased production mainly because zeolite significantly increased the effective number of units per unit area.Especially during jointing and subsequent growth period,the addition of zeolite can significantly reduce the rate of rice stem and tiller ineffective apoptosis.(2)In both irrigation modes,zeolite significantly reduced paddy field water consumption and improved rice water productivity.During the two years,10 t · hm-2 zeolite reduced water consumption in paddy fields by 6.3%~7.5% and 5.2%~11.2% and increased water productivity by 25.0%~36.1% and 18.0%~34.7%,respectively.The addition of zeolite can further increase its water-saving potential.(3)Increasing the application of zeolite(5~10 t · hm-2)can increase the available phosphorus content in the top soil of the paddy field during the whole growth period and the accumulation of phosphorus in the above-ground parts of the rice plant,promote the transfer and absorption of phosphorus nutrients in the plant up to 10 t · hm-2zeolite can significantly increase the available phosphorus content in the soil during the whole growth period,the phosphorus transport of rice leaves and stems,and the increase of phosphorus in rice panicles.Compared with submerged irrigation,dry-wet alternate irrigation can increase the available phosphorus content in the soil during all growth periods except the tillering stage and the total phosphorus accumulation in plants above the whole growth period and the accumulation of phosphorus in rice ears,and promote the rice plant absorption and utilization of nutrients.In addition,increasing the application of zeolite in flooded and alternately dry and wet paddy fields can also increase soil available phosphorus content in the basal fertilizer stage,tiller fertilizer stage,and panicle fertilizer stage,especially in the tiller fertilizer and fertilization stages.Finally,from the path analysis,zeolite significantly increased the available phosphorus content in the soil during the critical period,increased the plant's absorption of soil phosphorus,and finally increased rice yield.(4)Under different irrigation modes,increased application of zeolite(5~10 t · hm-2)can increase the available potassium content in the top soil of the paddy field during the entire growth period,and the application of zeolite under alternating dry and wet irrigation on soil the improvement effect is more obvious.Increasing the application of zeolite(5~10 t · hm-2)can increase the potassium accumulation in the aerial parts of rice plants,and promote the transfer of potassium from various organs of the plant to the ladle.Significantly increase the potassium transport of rice leaves and stalks and the increase of potassium in rice panicles.Compared with submerged irrigation,dry-wet alternate irrigation increased the amount and transfer rate of potassium in leaves and stalks,and decreased the amount of potassium accumulated in leaves and stalks during yellow ripening,thereby increasing the distribution ratio of potassium accumulation in rice panicles.In addition,increasing the application of zeolite in flooded irrigation and alternating dry and wet paddy fields can also significantly increase the soil available potassium content in the basal fertilizer period,tiller fertilizer period,and panicle fertilizer period.Finally,from the path analysis,we can see that the increase in rice production is because zeolite significantly increased the available potassium content in the soil during the K+ sensitive period,and increased the accumulation of potassium in the plant at the critical period.(5)According to the structural equation model(SEM),the accumulation of dry matter above ground during tillering and fertilization periods,and the accumulation of total phosphorus and total potassium above ground during fertilization periods have the greatest impact on yield.Among the indicators that have the greatest effect on the total output,zeolite has a very obvious effect on improving each indicator.It can be seen that the fundamental reason for the increase in rice yield is that zeolite significantly increased the dry matter accumulation in the shoots and tillers and the total phosphorus and potassium accumulation in the shoots.In summary,the addition of 10 t · hm-2 zeolite in the paddy field under the alternating dry and wet irrigation mode can not only reduce rice water consumption,improve rice water productivity and rice yield,but also increase soil available phosphorus and available potassium to promote the absorption and transfer of plant nutrients and provide a new way to reduce the consumption of phosphorus and potassium resources in the rice production system and improve the ecological environment while achieving high and stable yields. |
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